3D or multilayer weaving of fiber structures for constituting the fiber reinforcement of a composite material part, e.g. such as an aeroengine blade, is performed in a Jacquard type loom, the weaving consisting in inserting weft yarns so as to create a pattern between warp yarns. The warp yarns are organized in the harness of the loom as a plurality of layers and of columns that are manipulated by the loom so as to enable weft yarns to be inserted in compliance with the weaving pattern(s) programmed in the loom. The weft yarns are inserted in columns between the warp yarns.
In order to enable each column of weft yarns to be inserted while weaving the fiber structure, a warp yarn take-up system is associated with the loom. This system, which is located downstream from the loom, serves to hold all of the warp yarns together in a clamping device and to enable the warp yarns to advance through a determined distance after each column of weft yarns has been inserted.
Thus, when beginning new weaving of a fiber structure, it is necessary to clamp the warp yarns downstream from the loom. In addition, in the context of fabricating a series of fiber structures, e.g. fiber structures for forming reinforcement for turbine engine blades, it is necessary for the warp yarns to be clamped between each of the fiber structures.
The clamping device normally used is made up of two clamps 10 and 11, as shown in FIG. 10, with all of the warp yarns 21 that come from the warp yarn layers leaving the loom being held between them. The precise arrangement of the warp yarns or strands in layers and columns as defined in the harness of the loom is then upset in a bundle of disorganized yarns or strands between the clamps 10 and 11.
This disorganization of the warp yarns where they are clamped downstream from the loom leads to undesirable and uncontrolled sliding between the warp yarns, thereby disturbing the weaving within the fiber structure and harming its quality. The thicker the fiber structure, the greater the number of warp yarns and the greater the number of warp yarn layers that are needed for weaving. By way of example, it is necessary to use about 4000 warp yarns arranged in 20 layers in order to weave a fiber structure that is to form the fiber reinforcement of an aeroengine fan blade. The impact of the clamping on disorganizing the warp yarns is increased with increasing number of warp yarn layers.
In order to reduce this impact, the distance between the clamping device and the beginning of the woven fiber structure is increased. Nevertheless, that leads to a significant loss of yarn when cutting the yarns in order to extract the fiber structure, and that loss significantly penalizes the cost of fabrication.